Supercooled molecules in molecular beams of ICl and IBr

The properties of molecular beams of ICl and IBr built by means of the seeded beam technique were investigated experimentally. The axial velocity distribution was measured in a pseudorandom time-of-flight experiment and the rotational state distribution was estimated from the focusing properties of the beam in an alternate gradient focusing system. From a comparison between the computer simulation of a focusing experiment and actual measured results, it can be stated that the population of the very lowest rotational states with rotational quantum numbers J = 0, 1, 2 do not deviate significantly from a Boltzmann distribution. The rotational temperature is not very different from the translational temperature and has a value between 1 and 3 K. Collision numbers which are a measure of the translational rotational relaxation, are estimated from the experimental results